672 SUMMARY OF CURRENT RESEARCHES RELATING TO 



y. General. 



Ant-Gardens.* — E. Ule has made some interesting observations on 

 the ant-gardens which abound on many woody plants in the Amazon 

 region. They are commonly spherical, and about the size of a walnut. 

 Several species of ants appear to collect the seeds of a number of plants 

 and 60w them in these nests, covering up the seedlings with humus when 

 they begin to germinate. In the structure of these " ant-epiphytes," the 

 roots and foliage display characters which especially adapt them for the 

 situation in which they grow, and promote the protection of the ants in 

 their nests. Quite a number of these epiphytes were found by Ule as 

 denizens of the ant-gardens, and nowhere else. These comprised 3 

 species of Araceae, 5 of Bromeliaceae, 5 of Gesneraceas, 1 of Moraceae, 

 2 of Piperaceae, and 1 of Cactaceaa. 



Contrivances for Distribution in Plants.f — M. Kronfeld discusses 

 the various ways in which seeds or fruits are distributed, — by a floating 

 apparatus, by the elasticity of the walls of the carpels, by adhering to 

 the fur of animals, &c, devoting the present instalment to a detailed 

 description of the contrivances for assisting carriage by the wind (anemo- 

 carps). The minute seeds of epiphytic Orchids are dispersed by means 

 of hygroscopic hairs. The twisted ovary, which afterwards becomes 

 straight, is a further assistance. In a very large number of plants — 

 Primulaceae, Labiatae, Asperifolieaa, Plantago, &c. — the wind shakes the 

 seeds out of the dry persistent calyx ; and this is the case with one genus 

 of Compositae, Lapsana, in which the calyx is almost entirely obsolete. 

 The seeds of Typha possess special contrivances for dispersion, not only 

 by the wind, but also by water and by animals. 



Osmotic Pressure as a Defence against Cold.J — M. d' Arson val at- 

 tributes the exemption of living plants from destruction by severe cold 

 to the very high osmotic pressure within the cell, which, as is well 

 known, prevents water from freezing. Beer-yeast, the pyocyanic bacillus, 

 and various pathogenic microbes, may retain their vitality even after 

 having been subjected, during several weeks, to the temperature of liquid 

 air. It has been shown that the pressure within the cells of certain 

 mould-fungi may exceed 160 atmospheres ; and it is possible, the author 

 suggests, that within micro-organisms it may amount to thousands of 

 atmospheres. 



B. CRYPTOGAMIA. 



Phyllotaxis in Musci and Florideae.§ — In certain genera of Mosses 

 — Dicranum, Aulacomnion, Polytrichum — H. Seckt has established the 

 law that each new segment of the apical cell is so formed that the inner 

 wall of the ri h segment is nearly parallel to the inner wall of the n-S rd 

 segment. The anodic encroachment (Vorgreifen) of the newly formed 

 membrane cannot therefore be original, but must be the result of a sub- 

 sequent displacement. The same is stated by the author to be the case, 



* Engler's Bot. Jabrb., xxx. (1901) Beibl. (38, pp. 45-52 (1 pi.), 

 t Stud. iib. d. Verbreitungsmittel d. Pflauzen, Tb. i. Windfriichtler, Leipzig^ 

 1900 (5 figs.). See Bot. Centralbl., lxxxvii. (1901) p. 5S. 

 % Comptes Rendus, cxxxiii. (1901) pp. 84-6. 

 § Beib. z. Bot. Centralbl., x. (1901) pp. 257-78 (2 pis.). 



